The resonator fiber optic gyroscope (RFOG) is a promising contender for next generation navigation gyroscopes. It has the potential to provide a navigation grade solution with the combination of low cost, small package size, and weight. The RFOG uses at least two laser beams as signal light waves, at least one of the laser beams propagates around a resonator coil in the clockwise (CW) direction and the other laser beam in the counter-clockwise (CCW) direction. In the operation of a resonant fiber optic gyroscope (RFOG), it is desirable to tune the frequencies of the laser light sources to the resonance frequencies of the fiber optic ring resonator. In tuning the frequencies, the resonance frequencies may be measured in the CW and CCW direction. The input beam frequencies may be compared and the difference between the input beam frequencies is proportional to the rotation rate of the resonator coil. However, an indicated output may be present when the gyroscope is not rotating. A measured output when no rotation is present contributes to bias instability. One of the major causes of bias instability in RFOGs is backscattered light from one signal light wave propagating in one direction through the resonator to where the light propagates in the other opposite direction through the resonator, where the input signal laser waves, and hence the backscattered, are close to the same frequency. Hence, in this case, the signal light in one direction is co-propagating with the light that is backscattered from the other signal light wave, and they are at the same or nearly same frequency. The presence of backscattered light may decrease the ability to sense rotation at low rotation rates and may increase bias instability.